Card with embedded IC and electrochemical cell

ABSTRACT

An IC card includes at least one plastic layer, a battery and at least one electronic device embedded in the plastic layer. The battery is electrically connected to the electronic device for providing power to the device. The battery includes an anode, a cathode, and at least one polymer matrix electrolyte (PME) separator disposed between the anode and the cathode. The PME separator includes a polyimide, at least one lithium salt and at least one solvent all intermixed. The PME is substantially optically clear and stable against high temperature and pressure, such as processing conditions typically used in hot lamination processing or injection molding.

CROSS REFERENCE TO RELATED APPLICATION

[0001] Not applicable.

STATEMENT AS TO FEDERALLY SPONSORED RESEARCH

[0002] Not applicable.

FIELD OF THE INVENTION

[0003] The invention generally a card including an embedded batteryinternally connected to electronics also embedded in the card.

BACKGROUND

[0004] The need for information cards that contain electronics such asintegrated circuits (IC) has been increasing as of late. The IC canprovide functions, such as for retrieving, processing, transmitting andstoring information. Such cards are generally referred to as “smartcards” which have potential application in a wide range of fields,including commerce, transportation, communication, identification, andsecurity.

[0005] It is known to incorporate batteries into cards to provide apower source for the electronic circuitry within. Having a batteryincorporated into the IC card allows for the storage of greater amountsof data, and further allows for improved processing capabilities.

[0006] Because of the difficulty of providing the energy required formost applications within the space constraints of a typical credit card,it is desirable to use battery types which provide the highest energydensity. Lithium batteries have been introduced into the market becauseof their high energy densities. Lithium is atomic number three on theperiodic table of elements, having the lightest atomic weight andhighest energy density of any solid material. As a result, lithium is apreferred material for batteries, having very high energy density.Lithium batteries are also desirable because they have a high unit cellvoltage of up to approximately 4.2 V, as compared to approximately 1.5 Vfor both Ni-Cd and Ni-MH cells. Lithium batteries can be either lithiumion batteries or lithium metal batteries. Lithium ion batteriesintercalate lithium ions in a host material, such as graphite, to formthe anode. On the other hand, lithium metal batteries use metalliclithium or lithium alloys for the anode.

[0007] Lithium batteries having solid polymer electrolytes represent anevolving alternative to lithium batteries having liquid electrolytes.Solid polymer electrodes are generally gel type electrolytes which trapsolvent and salt in pores of the polymer to provide a medium for ionicconduction. Typical polymer electrolytes comprise polyethylene oxide(PEO), polyether based polymers and other polymers which are configuredas gels, such as polyacrylonitrile (PAN), polymethylmethacrylate (PMMA)and polyvinylidine fluoride (PVDF). The polymer electrolyte generallyfunctions as a separator, being interposed between the cathode and anodefilms of the battery.

[0008] Lithium metal polymer (LMP) rechargeable batteries offer improvedperformance as compared to Li ion batteries, particularly highercapacity. LMP batteries result from the lamination/assembly of threetypes of main thin films: a film of positive electrode comprising amixture of a polymer and an electrochemically active material such aslithium vanadium oxide, an electrolyte film separator made of a polymerand a lithium salt, and a negative electrode film comprising metalliclithium or a lithium alloy.

[0009] Unfortunately, conventional batteries including lithium metal orlithium ion batteries lack the stability to be subjected to credit cardprocessing, which can include a temperature of 125 C to 140C, a pressureof 200 to 250 psi, and a dwell time of 5 to 15 minutes. Conventionalbatteries subjected to the above described card lamination conditionswill generally either catastrophically fail or experience a large shiftin operating parameters which would render them of no practical use. Asa result, although batteries have been disposed inside credit cards, alow temperature glue has been used to bind the battery to the card.

SUMMARY OF THE INVENTION

[0010] An IC card includes at least one plastic layer, a battery and atleast one electronic comprising device embedded in the plastic layer.The battery is electrically connected to the electronic comprisingdevice for providing power for the electronic comprising device. Thebattery includes an anode, a cathode, and at least one polymer matrixelectrolyte (PME) separator disposed between the anode and the cathode.The PME separator comprising a polyimide, at least one lithium salt andat least one solvent intermixed. The lithium salt is preferably in aconcentration of at least 0.5 moles of lithium per mole of imide ringprovided by said polyimide. The PME is substantially optically clear.

[0011] As used herein, the phrase “substantially optically clear”relative to the PME refers to a material being at least 90% clear(transmissive), preferably at least 95%, and most preferably being atleast 99% clear as measured by a standard turbidity measurement for 1mil normalized thick film at 540 nm. The high level of optical clarityof the PME evidences the homogeneity of the PME comprising itsrespective components (polyimide, salt and the solvent) as anysignificant phase separation would reduce optical clarity.

[0012] The anode can include lithium ion intercalation material orlithium metal including lithium metal alloys. A repeat unit weight perimide ring of the polyimide can be no more than 350, no more than 300,or no more than 250. The polyimide is soluble at 25 C in at least onesolvent selected from the group consisting of N-methylpyrrolidinone(NMP), dimethylacetamide (DMAc) and dimethylformamide (DMF).

[0013] The ionic conductivity of the PME at 25° C. is at least 1×10⁻⁴S/cm, and is preferably at least 3×10⁻⁴ S/cm.

[0014] The Li salt can be selected from a variety of salts. For exampleLiCl, LiBr, Lil, LiClO₄, LiBF₄, LiAsF₆, LiPF₆, LiCF₃SO₃, LiBOB,LiN(CF₃SO₂)₂, and lithium bis(trifluorosulfonyl)imide (LiTFSI) can beused.

[0015] The cathode can comprise an ion conducting polymeric binderintermixed with an intercalation material. In this embodiment, thepolymeric binder can comprise at least one polyimide, including the samepolyimide comprising the PME.

[0016] The battery can provide no significant change in open circuitvoltage (OCV) or capacity following heating at 125° C. for at least 5minutes while under a pressure of at least 250 psi. As used herein, thephrase “no significant change in open circuit voltage (OCV) or capacity”following a given heat and/or pressure cycle, refers to a shift in theopen circuit voltage and capacity of the battery of no more than 15%,preferably less than 10%, and more preferably less than 5%.

[0017] For example, a lithium metal battery having a lithium vanadiumoxide comprising cathode was found to provide a shift in OCV of 1.4% anda commensurately small reduction in capacity following a typical creditcard lamination process comprising a temperature of 140 C for 15 minutesunder a pressure of 220 psi. Moreover, batteries formed using the PMEare quite flexible and can exceed ISO standards ISO/IEC 10373 and 14443.

[0018] The battery can be a primary battery or secondary battery. Thebattery is preferably a bicell. The IC card can utilize a packagecomprising packaging material surrounding said battery to form apackaged battery, the packaging material laminated by an exterior binderadhesive to all exterior surfaces of the battery. In another embodiment,a package including packaging material surrounds the battery and a framehaving an opening to accommodate the battery therein is used to form apackaged battery, wherein the battery is disposed within the opening.This embodiment provides highly planar batteries, such as a thicknessuniformity throughout within ±1 mil.

[0019] The IC card can include an exterior binder adhesive disposedbetween the packaged battery and the plastic layer to bind said packagedbattery to the plastic layer, wherein the exterior binder adhesive isactivated at a temperature of at least 100 C. An interior binderadhesive can be use to seal the battery, wherein the interior binderadhesive has an activation temperature which is lower than theactivation temperature of the exterior binder adhesive. The IC card canprovide a thickness uniformity throughout within ±1 mil. In addition,the IC card can comply with ISO testing criteria for bending, flex, andtorsion according to ISO standards ISO/IEC 10373 and 14443 withoutinducing any visually detectable delamination.

[0020] A method of forming a card including embedded electronicsincludes the steps of providing a battery including an anode, a cathode,and at least one polymer matrix electrolyte (PME) separator disposedbetween the anode and the cathode. The PME separator comprises apolyimide, at least one lithium salt and at least one solventintermixed, the PME being substantially optically clear. The battery andat least one electronic comprising device are embedded in at least oneplastic layer, the battery being electrically connected to theelectronic comprising device. The embedding process can be a laminationprocess, wherein a temperature of least 110° C. for at least 5 minutesunder a pressure of at least 200 psi is used for the lamination process,the battery providing a shift in open circuit voltage or capacity ofless than 10% following the lamination process. The laminationtemperature can be at least 130° C. for at least 10 minutes under apressure of at least 230 psi, with the battery again providing a shiftin open circuit voltage or capacity of less than 10% following thelamination process.

[0021] The embedding process can comprise an injection molding process,the battery providing a shift in open circuit voltage or capacity ofless than 10% following an injection molding process comprising atemperature of at least 200° C. and a pressure of at least 1000 psi. Theinjection molding temperature can be at least 250 C and the pressure canat least 5000 psi, with the battery providing a shift in open circuitvoltage or capacity of less than 10% following the injection moldingprocess.

[0022] The battery can be formed by laminating only two layers. In thisembodiment of the invention, a first layer is the PME disposed on thecathode and the second layer is the anode.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] A fuller understanding of the present invention and the featuresand benefits thereof will be accomplished upon review of the followingdetailed description together with the accompanying drawings, in which:

[0024]FIG. 1(a)-(m) illustrates the repeat unit structure for severalsuitable polyimides, according to an embodiment of the invention.

[0025]FIG. 2 is a table illustrating ionic conductivity and theresulting film composition at 20.5° C. for a PME comprising thepolyimide shown in FIG. 1(m), LiTFSi salt (2.2×) and the solvent gammabutyrolactone (GBL), according to an embodiment of the invention.

[0026]FIG. 3(a)-(d) are plots of the ionic conductivity of a PMEcomprising the polyimide shown in FIG. 1(m) and the lithium salt LiTFSi(2.2×) as a function of solvent load and temperature for the solventsTMS, PC, GBL, and NMP, respectively.

[0027]FIG. 4 is a plot of ionic conductivity of a PME comprising thepolyimide shown in FIG. 1(m) and a lithium salt (LiTFSi; 2.2×) as afunction solvent/polyimide ratio at 20 C, where the solvent is GBL.

[0028]FIG. 5(a) is FTIR data for an exemplary polyimide without theaddition of a Li salt or any solvent.

[0029]FIG. 5(b) is FTIR data for an exemplary Li salt.

[0030]FIG. 5(c) is FTIR data for the exemplary polyimide whose FTIR datais shown in of FIG. 5(a) intermixed with and the exemplary Li salt whoseFTIR data is shown in FIG. 5(b) evidencing the emergence of a doubletabsorption peak at between about 1630 cm⁻¹ and 1690 cm⁻¹.

[0031]FIG. 6 is a table which includes dianhydrides and aromaticdiamines that can be used for making polyimides presented herein.

[0032]FIG. 7 shows an assembly process for forming an electrochemicalbicell which is ready for packaging, according to an embodiment of theinvention.

[0033]FIG. 8 shows an assembly process for packaging the electrochemicalbicell produced by the assembly process shown in FIG. 7.

[0034]FIG. 9 shows an assembly process for embedding a packagedelectrochemical bicell produced by the assembly process shown in FIG. 8and an electronic flex circuit embedded inside a PVC card, according toan embodiment of the invention.

[0035]FIG. 10(a) is a SEM evidencing a defect free PME.

[0036]FIG. 10(b) is a SEM showing a smooth and uniform interface betweena PME disposed on a lithium vanadium oxide (LVO) comprising cathodelayer.

[0037]FIG. 11 shows the charge/discharge profile of a typical cellaccording to the invention, the cell including a lithium vanadium oxidecathode, a Li metal anode and a PME separator, according to anembodiment of the invention.

DETAILED DESCRIPTION

[0038] The invention describes an IC card including at least oneelectronic device and battery embedded therein. The battery iselectrically connected to the electronic comprising device, such as anintegrated circuit (IC) for providing power for the device. The batterycomprises an anode, a cathode and a substantially optically clearelectrolyte separator matrix between the anode and cathode.

[0039] The separator matrix includes a polyimide, a lithium salt andsome solvent. The lithium salt is in a concentration of at least 0.5moles of lithium per mole of imide ring provided by the polyimide. Thesolvent is generally a low molecular weight, low viscosity liquid whichswells the polyimide at low concentration and at a sufficiently highconcentration allows the polyimide, salt and the solvent to becomehomogeneously mixed. As used herein, the substantially optically clearelectrolyte separator matrix is referred to as a “polymer matrixelectrolyte” or PME.

[0040] The battery can be both a lithium ion and lithium metal battery.Unlike gel polymer electrolytes, once the PME is formed, there isgenerally no free solvent or identifiable pores. For example, using aSEM at a 50 A resolution, no pores in the PME can be identified.Instead, the solvent is integrated with the polymer and the lithium saltin a homogeneous and substantially optically clear matrix. In addition,unlike conventional gel polymers where the polymer only providesmechanical support, the polymer, salt and solvent comprising the PME allparticipate in ionic conduction.

[0041] The PME provides high current carrying capacity, cyclingstability and maintains this performance level across a wide temperaturerange, such as at least from −40° C. to 100° C. For example, the PME canwithstand high temperatures and pressures with small changes in opencircuit voltage and capacity, such as the conditions generally used inthe hot lamination processes used in credit card manufacturing, or evena typical injection molding process. For example, hot laminationprocesses used in credit card assembly generally utilize a temperatureof about 115-150° C. for typically 5 to 15 minutes under a pressure ofabout 200-250 psi. The performance of batteries formed using the PMEexperience no significant change in open circuit voltage (OCV) orcapacity from the temperature and pressure conditions provided by atypical credit card lamination process.

[0042] As used herein, the phrase “no significant change in OCV andcapacity” following a lamination or molding process refers to a batteryincluding the PME which demonstrates an OCV and capacity which shiftsless than 15%, preferably less than 10%, and more preferably less than a5% following the lamination or molding process.

[0043] For example, a lithium metal battery having a lithium vanadiumoxide comprising cathode was found to provide a shift in OCV of 1.4% anda commensurately small reduction in capacity following a laminationprocess comprising a temperature of 140 C for 15 minutes under apressure of 220 psi. Moreover, batteries formed using the PME are quiteflexible and can exceed ISO standards ISO/IEC 10373 and 14443.

[0044] Thus, PME based batteries are particularly well suited for useinside credit cards, smart labels, and other small devices which requirehigh temperature/high pressure lamination processing and can benefitfrom an on board power supply. Regarding credit card and relatedapplications for the invention, the high level of battery stability toboth mechanical and thermal stresses provided by the PME permitsbatteries according to the invention to withstand harsh credit cardprocessing conditions.

[0045] The PME is generally based on one or more polyimides, whichunlike other polymer-based electrolytes, participate in ionicconductivity through the presence of imide rings and other polar groups.Other polymer types which include highly polar groups having functionalgroups that can complex with lithium salts and participate in ionicconduction include polybenzimidazoles and polyamide-imides. Accordingly,these polymer types may also include species useful in forming a PME.

[0046] Polyimides are reaction products of a condensation reactionbetween diamines and dianhydrides to initially form a poly (amic-acid)intermediate. Either or both the diamine and dianhydride reagent can bemixture of diamine or dianhydride species. The poly amic-acidintermediate is then converted to a fully imidized polyimide.

[0047] The properties of the resulting polyimide formed depend on theselection of the particular diamines and dianhydride monomers.Polyimides are generally known to provide high thermal stability,chemical resistance and high glass transition temperatures, such as 200°C. to more than 400° C.

[0048] The current invention has identified polyimides distinct fromthose disclosed in the '672 patent and has found the addition of solventto some of these distinct polyimides can result in the formation of aPME. Some of the polyimides identified herein provide represent newlysynthesized polymers. Unlike the polymers disclosed in '672, thepolymers disclosed herein form a substantially homogeneous matrixmaterial (PME) when combined with an appropriate concentration of saltand the solvent. The homogeneity is evidenced by the high level ofoptical clarity provided by the PME as noted in Example 1. In contrast,the electrolytes disclosed in '672 are non-homogeneous mixture, asevidenced by their opaqueness also shown in Example 1 which isindicative of phase separation of the respective components.

[0049] The Inventors have identified and synthesized improved polyimidesfor use in forming PMEs by qualitatively relating certain polymerparameters to ionic conductivity. Imide ring density is believed toexplain why polyimide films, when loaded with lithium salt, showsignificant ionic conductivity, even in the absence of solvent. Repeatunit weight per imide ring is one measure of imide ring density and iscalculated by dividing the molecular weight of the entire repeat unit ofthe respective polyimides by the number of imide rings within therespective repeat units.

[0050] Imide rings may provide the equivalent of a high dielectricconstant to materials because of the high electron density provided bythe rings. Accordingly, it is believed that the interaction between theimide rings and the lithium ion is a factor in determining the ionicconductivity of a PME. Thus, improved polyimides for use as PMEs can begenerally selected for further consideration by first calculating thenumber of imide rings (and to a lesser degree other highly polar groups,such as sulfone, carbonyl and cyanide) per molecular repeat unit in agiven polyimide. The more imide ring function present per unit weight,the higher the average dielectric strength equivalence of the polymer.Higher equivalent dielectric strength is believed to generally lead toimproved salt interaction, which can improve the ionic conductivity ofthe PME.

[0051] Alternatively, a quantity roughly inverse to imide ring densityreferred to as repeat unit weight per imide ring can be calculated toalso compare the relative concentration of imide rings in polyimides. Asthe repeat weight per imide ring decreases, imide rings become anincreasingly greater contributor to the repeat unit as a whole. As aresult, as the repeat weight per imide ring decreases, the equivalentdielectric constant and ionic conductivity of the polyimide generallyincrease.

[0052] Polyimides which provide high helium permeability may generallyproduce higher ionic conductivity and thus form better PMEs. At 25° C.,the measured He permeability of most polyimides according to theinvention has been found to be at least 20 barrers. The He permeabilitycan be at least 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75 or 80barrers, or more.

[0053] Helium permeability may be measured in the following suggestedmanner. The gas permeability (GP) of a gas component through a givenfilm having a thickness (I) and area (A) can be determined by applying apressure (p) across the film which is equal to the upstream pressureminus the downstream pressure of the gas component and measuring theresulting steady state rate of gas flow (f) permeating through the filmat STP.

GP=(fI)/(Ap)

[0054] Preferred units for GP is (cm²)(sec)⁻¹(cmHg), where 1 barrer isdefined as the GP multiplied by 10¹⁰.

[0055] It is believed that the maximum ionic conductivity of the PMEgenerally occurs when the polyimide/salt/solvent combination creates acompletely homogenous, clear matrix. Any phase separation is expected toreduce the ionic conductivity values because phase separation wouldincrease the tortuosity within the PME.

[0056] The maximum electrolyte conductivity of the PME at a giventemperature generally occurs when the polyimide/salt/solvent matrix hasa ratio within a specified range. The optimum salt concentration isgenerally in the range of 0.5 to 2.0 moles Li per mole of imide ring fora polyimide. Too little salt generally does not provide a sufficientnumber of ions to contribute to the charge transfer. Too much saltgenerally leads to phase instability and possible precipitation of thepolyimide and resulting loss of homogeneity which can be verified by aloss in optical clarity.

[0057] The solvent is believed to play the role of a swelling agent forthe polymer to move the backbone chains slightly apart and thereforeenables greater ionic diffusion coefficients. The solvent also acts as asolvation carrier for the ions. Typically the solvent is chosen to alsobe stable within the limitations of the type of battery chosen. Forexample, for a lithium ion type battery the solvent must be stable up tothe reduction potential of lithium metal. The amount of solvent can beoptimized depending upon the either the conductivity desired or thesoftening point of the matrix at some required temperature. Solvents canbe selected from a group of solvents including gamma butyrolactone(GBL), propylene carbonate, N-methylpyrrolidinone (NMP),tetrahydrothiophen-1,1-dioxide (TMS), polycarbonate (PC) and dimethylformamide (DMF).

[0058]FIG. 1(a)-(m) illustrates the repeat unit structure for severalpolyimides, according to an embodiment of the invention. The repeat unitfor a polymer referred to as Polyimide A is shown in FIG. 1(a). Thispolyimide can be formed by reacting PMDA [89-32-7] with TMMDA[4037-98-7]. This high molecular weight polymer is soluble in NMP for alimited number of hours thus a lithium salt containing electrolyte couldnot be produced.

[0059] The repeat unit for the polymer referred herein to as Polyimide Bis shown in FIG. 1(b). This polyimide can be formed by reacting 90 mole% PMDA [89-32-7], 10 mole % 6FDA [1107-00-2] dianhydrides and thediamine TMMDA [4037-98-7]. The polymer formed was soluble indefinitelyin NMP at 20% by weight.

[0060] The repeat unit for the polymer referred herein to as Polyimide Cis shown in FIG. 1(c). This polyimide can be formed by reacting 85.7mole % PMDA [89-32-7], 14.3 mole % 6FDA [1107-00-2] and TMMDA[4037-98-7]. The polymer formed was soluble indefinitely in NMP at 20%by weight.

[0061] The repeat unit for the polymer referred herein to as Polyimide Dis shown in FIG. 1(d). This polyimide can be formed by reacting 80 mole% PMDA [89-32-7], 20 mole % PSDA [2540-99-0] and TMMDA [4037-98-7]. Thepolymer formed was soluble indefinitely in NMP at 20% by weight.

[0062] The repeat unit for the polymer referred herein to as Polyimide Eis shown in FIG. 1(e). This polyimide can be formed by reacting BPDA[2421-28-5] and 3,6diaminodurene [3102-87-2]. The polymer formed wassoluble indefinitely in NMP at 20% by weight.

[0063] The repeat unit for the polymer referred herein to as Polyimide Fis shown in FIG. 1(f). This polyimide can be formed by reacting 6FDA[1107-00-2] and 3,6-diaminodurene [3102-87-2]. The polymer formed wassoluble indefinitely in NMP at 20% by weight and is also soluble inacetone, GBL, DMAc, and DMF.

[0064] The repeat unit for the polymer referred herein to as Polyimide Gis shown in FIG. 1(g). This polyimide can be formed by reacting PSDA[2540-99-0] and TMMDA [4037-98-7]. The polymer formed was solubleindefinitely in NMP at 20% by weight and is soluble in GBL.

[0065] The repeat unit for the polymer referred herein to as Polyimide His shown in FIG. 1(h). This polyimide can be formed by reacting 6FDA[1107-00-2] and TMMDA [4037-98-7]. The polymer formed was solubleindefinitely in NMP at 20% by weight and is soluble in acetone, GBL,DMAc, and DMF.

[0066] The repeat unit for the polymer referred herein to as Polyimide Iis shown in FIG. 1(j). This polyimide can be formed by reacting BPDA[2421-28-5] and 4,4′-(9-fluorenylidene)dianiline [15499-84-0]. Thepolymer formed was soluble indefinitely in NMP at 20% by weight.

[0067] The repeat unit for the polymer referred herein to as Polyimide Jis shown in FIG. 1(j). This polyimide can be formed by reacting PMDA[89-32-7], 33.3 mole % TMPDA [22657-64-3] and 66.7 mole % TMMDA[4037-98-7]. The polymer formed was soluble indefinitely in NMP at 20%by weight.

[0068] The repeat unit for the polymer referred herein to as Polyimide Kis shown in FIG. 1(k). This polyimide can be formed by reacting PMDA[89-32-7] and DAMs [3102-70-3]. The polymer formed was soluble only fora short time in NMP.

[0069] The repeat unit for the polymer referred to herein as Polyimide Lis shown in FIG. 1(I). This polyimide can be formed by reacting PMDA[89-32-7] and 4-isopropyl-m-phenylenediamine [14235-45-1]. The polymerformed was soluble indefinitely in NMP at 20% by weight.

[0070] The repeat unit for the polymer referred herein to as Polyimide Mis shown in FIG. 1(m). This polyimide can be formed by reacting PMDA[89-32-7], 33.3 mole % DAMs [3102-70-2] and 66.7 mole % TMMDA[4037-98-7]. The polymer formed was soluble indefinitely in NMP at 20%by weight.

[0071] The PME includes at least one lithium salt. High PME ionconductivities are generally achieved using a high salt content, such asfrom about 0.5 to 2.0 moles of Li per mole of imide ring for polyimidepolymers. However, the concentration of lithium salt can be 0.6, 0.7,0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0, 2.1,2.2, 2.3, 2.3, 2.4 or 2.5 moles Li per mole of imide ring of thepolyimide.

[0072] Salt concentrations are also described herein as a ratio of theweight of the salt to weight of the polymer (e.g. polyimide) excludingthe salt. For example, a 1× concentration corresponds to an equal amountof salt and polymer, while a 2×salt concentration corresponds to twicethe salt concentration as compared to the polymer concentration. Thelithium salt can generally be any lithium salt known in the art.Preferably, lithium salts are chosen from LiCl, LiBr, LiI, Li(ClO₄),Li(BF₄), Li(PF₆), Li(AsF₆), Li(CH₃CO₂), Li(CF₃ SO₃), Li(CF₃ SO₂)₂N,Li(CF₃ SO₂)₃, Li(CF₃ CO₂), Li(B(C₆H₅)₄, Li(SCN), and Li(NO₃), lithiumbis(trifluorosulfonyl)imide (LiTFSI), LiBOB, and LiSCN. Preferably, thesalt is either Li(PF₆) or LiTFSi.

[0073] Polyimide structures other than the exemplary structures shown inFIG. 1 can be good candidates for use in forming a PME matrix.Characteristics that a good Pl should display, such as solubility in NMP(or other suitable solvent) to at least 20 wt % and a low repeat unitweight per imide ring can be a first criteria. However, the solubilityof the PI itself or the solution stability when combined with a highconcentration of a lithium salt applicable for battery applications isnot easily predictable.

[0074] Behavior in solution can not generally be ascertained by simplylooking at the polymer repeat unit structure. However, it can bedetermined from looking at the structure whether the polymer willpossibly be crystalline, or whether it would have a high or low relativedensity in the solid phase. The polyimides are preferablynon-crystalline, low-density repeat structures because they would bemost likely to be very soluble. However, changing a single side groupfrom a methyl to an ethyl can cause the properties of the PI to bechanged from useful to of no use. A suggested screening procedure toidentify alternative polyimides for battery applications is to take apolyimide that is known to have a good solubility in the solvent itselfand then try to introduce the lithium salt at 0.5 mole Li per imide ringor more and see if (i) the resulting PI/salt/solvent solution is clearand homogenous for a few hours and (ii) the film cast from that solutionremains substantially clear when most of the solvent (e.g. 95%) has beenevaporated.

[0075]FIG. 2 is a table illustrating the ionic conductivity at 20.5° C.and the corresponding film composition for a polyimide based PMEcomprising the polyimide shown in FIG. 1(m), LiTFSi salt (2.2×) and thesolvent GBL, according to an embodiment of the invention. Roomtemperature ionic conductivity values for PME films were calculated frommeasured impedance using a complex impedance analyzer. Measurementsusing the impedance analyzer were made in the frequency range of 1 MHzto 0.1 Hz. A value for the resistance of the film, R, was taken as theintercept with the real axis of a Nyquist plot, or by an extrapolationof the high frequency portion of the response curve to the real axis.Measurements were also made on an LCR meter at a fixed frequency of 10kHz where the resistance values were read directly. The ionicconductivity was calculated using the formula:

C(Seimens/centimeter)=t/R×10⁻⁴

[0076] where t is film thickness in microns and R is the measured filmresistance in Ohms.

[0077] As shown in FIG. 2, for the PMEs tested, the maximum ionicconductivity at 20.5° C. was about 1×10⁻⁴ S/cm for a 1×saltconcentration and 4×10⁻⁴ S/cm for a 2.2× concentration, where the PMEfilm comprised 37.9% GBL. The lower table portion shown in FIG. 2 showsthe minimum solvent level required to provide a conductivity of 1×10⁻⁴S/cm for 1.0, 1.4, 1.8 and 2.2×salt concentrations.

[0078] The range of solvent in FIG. 2 is expressed as the solvent/PIratio and runs from about 1 to about 2. The lower value is where onearbitrarily defines a conductivity as being “high enough” to be ofinterest, such as 1.0E⁻⁴ S/cm. The maximum conductivity was found tooccur between a solvent/PI ratio of 1.5 to 2.0 depending upon the saltconcentration.

[0079] The upper solvent/PI limit near 2 is controlled by the mechanicalproperties of the PME. At a high solvent/PI ratio the PME film becomesvery soft and may not be usable over an extended temperature range as aseparator for a battery. Applied to lithium metal batteries, As apractical matter, the solvent is chosen to be moderately stable againstlithium metal, high boiling (>150 C), capable of dissolving the chosensalt and swelling the PI, and finally it should have a low viscositywhich promotes a high conductivity for the salt/solvent combination byitself, as well as for the PME.

[0080] To optimize the respective PI, salt and solvent concentrations, asuggested procedure is described below in a first step, a PI species isselected which is soluble in an appropriate solvent, such as NMP or GBL.All the polyimides shown in FIG. 1 except the polyimide shown in FIG.1(k), are soluble in NMP. In the second step, a desired lithium salt isselected and an initial concentration is selected, such as a mass ratiothat gives one lithium ion per imide ring provided by the selected PI.The solvent concentration can then be varied from a solvent/PI ratio ofabout 0.8 to 2.0 while measuring the ionic conductivity for severalsolvent/PI data points in between. This can be repeated at saltconcentrations both higher and lower. There are generally severalcombinations of PI/salt/solvent by mass that will give similar ionicconductivities, such as within a factor of two.

[0081]FIG. 3(a)-(d) are plots of the ionic conductivity of a PMEcomprising the polyimide shown in FIG. 1(m) and the lithium salt LiTFSi(2.2×) as a function of solvent load and temperature for the solventsTMS, PC, GBL, and NMP, respectively. These curves generally do not showa clear conductivity maximum because the salt content was 2.2×, and as aresult, the amount of solvent needed to provide the maximum ionicconductivity was large and generally impractical.

[0082]FIG. 4 is a plot of ionic conductivity of a PME comprising thepolyimide shown in FIG. 1(m) the lithium salt (LiTFSi; 2.2×) as afunction solvent/polyimide ratio at 20° C., where the solvent is GBL.The ionic conductivity is seen to increase for increasing solvent topolyimide ratio up to about a GBL/polyimide ratio of about 1.5, wherethe ionic conductivity levels off at a value of about 7×10⁻⁴ S/cm.

[0083] The ionic conductivity of PMEs based on polyimides is believed tobe related to the degree the polyimides associate with alkali salts,particularly Li salts. This association is likely related to theformation of complexes between polar groups (e.g. imide and benzene) ofthe polyimide and the salt. Evidence for this association can be foundby measuring the absorption frequencies displayed by the polymer whenintermixed with the salt and comparing this data to the absorptionfrequencies displayed by the polyimide and the salt by themselves.

[0084] For a polyimide, characteristic absorption frequencies arebelieved to be related to the imide rings and benzene rings thatcomprise the polyimide backbone. These absorption peaks are at about1778 cm⁻¹ and 1721 cm⁻¹ for the imide ring and 730 cm⁻¹ for the benzenering. Common Li salts, including LiPF₆, LiBOB, LiI and LiTFSi do notshow absorption at these frequencies, nor any absorption peaks betweenabout 1630 and 1690 cm⁻¹. However, when certain polyimides whichassociate strongly with Li salts are combined with those salts, theresulting polyimide/salt film show the emergence of a very strongdoublet with a first peak at about 1672 cm⁻¹ and a second peak at about1640 cm⁻¹

[0085] The first absorption frequency is present when a significantconcentration of salt is in the polyimide film, such as at least 33 wt.%, but does not change significantly with increasing salt concentration.Thus, this peak can be used to indicate the interaction, provided asufficient salt concentration is present. The magnitude of the secondpeak is nearly proportional to the ratio of the Li ion concentration tothe imide rings and can be used to assess the extent of the interactionbetween the polyimide and the salt.

[0086] Polymers other than polyimides which provide a high relativelocal electron density (e.g. comparable to electron density adjacent toimide rings in polyimides) and the potential for charge separation dueto multiple bond conjugation may form a polymer/salt complex and displaycharacteristic absorption peaks based on the complex formed, providedthey are soluble. Thus, absorption spectroscopy, such as FTIR can beused to identify these soluble non-polyimide polymers which showevidence of complex formation for use as a PME.

[0087]FIG. 5(a) is FTIR data for an exemplary polyimide, the polyimideshown in FIG. 1(c), without the addition of a Li salt or any solvent.Absorption peaks related to the imide rings are shown at about 1778 cm⁻¹and 1721 cm⁻¹ and at 730 cm⁻¹ for the benzene ring. This polyimide doesnot show any detectable absorption peaks between about 1630 and 1690cm⁻¹.

[0088] Common Li salts, including LiPF₆, LiBOB, Lil and LiTFSi do notshow absorption between 1630 and 1690 cm⁻¹. FIG. 5(b) shows an FTIR forLiBOB confirming the absence of infrared absorption between about 1630and 1690 cm⁻¹.

[0089]FIG. 5(c) shows the FTIR the polyimide shown in FIG. 1(c) combinedwith LiBOB. The resulting polyimide electrolyte shows a very strongdoublet with a first peak at about 1672 cm⁻¹ and a second peak at 1640cm⁻¹.

[0090] Thus, FTIR measurements taken from exemplary PMEs according tothe invention provide evidence that the lithium salt forms a complexwith the imide rings of the polyimide. This is likely one of the mainreasons why the polyimide/lithium salt combination, in a dry film, hasno apparent structure or crystallinity. The lack of crystallinity can beshown by a flat DCS trace. This evidence has also been found of aninteraction between the lithium salt and the polyimide as the PME filmis optically clear whether as a free standing film or as an overcoatedfilm.

[0091] The card cell battery can be a primary or rechargeable battery.The battery can utilize a lithium ion or lithium metal anode. In thecase of a rechargeable battery, contactless charging operations known inthe art, such as using inductive coupling can be used to provide energyfrom an external power source to recharge the battery over the airprovided appropriate reception devices are provided by the card cell.

[0092] In a preferred embodiment, a lithium metal battery having a PMEis formed. In this embodiment, the anode can be formed from lithiummetal or a lithium alloy. Lithium alloys can include lithium-aluminum,lithium-aluminum-silicon, lithium-aluminum-cadmiumlithium-aluminum-bismuth, lithium-aluminum-tin or lithium-titaniumoxide. The lithium content in these lithium alloys may be up to 99.98wt. %. The overall lithium content in the anode is based on the requiredcapacity of the battery.

[0093] The cathode material for the lithium metal battery can comprisean ionic conductive polymer binder, such as the polyimides describedherein, an electronically conductive material (e.g. graphite), and anelectrochemically active material. The electrochemically active materialis preferably selected from MnO₂, the various lithium vanadium oxides(Li_(x)V_(y)O_(z)), lithium transition metal oxides, such asLi_(x)Mn_(y)O_(z) (e.g. LiMn₂O₄), LiCoO₂, LiNiO₂, Li₄Ti₅O₁₂,LiV_(x)O_(y), and other materials such as metal sulfides (e.g. TiS₂) andLiFePO₄. Similarly, cathodes and anodes in the case of Li ion batteriespreferably include polyimides as binder matrices, such as thosedisclosed herein. For the Li ion or lithium metal battery, the anode,cathode and PME separator can all include the same or differentpolyimides.

[0094] Polyimides are generally prepared by reacting one or morediamines and one or more dianhydride monomers in a step-wisecondensation reaction. Preferred diamines and dianhydrides are shown inFIG. 6.

[0095] The purity of the monomeric reactants has been found to beimportant. Aromatic diamines are known to be air sensitive. Thus, apurification process generally includes removing a portion of theoxidized diamine material. Following purification, aromatic diaminestypically become white. However, absolutely pure diamines are difficultto achieve, and usually unnecessary. Recrystallization of the diaminefrom a mixture of alcohol and water has been found to be both effectiveand sufficient. The collected crystals are preferably dried under avacuum because the water used for crystallization may not be easilyremovable at room temperature.

[0096] Dianhydrides are also preferably purified and can be purifiedusing at least two methods. A preferred purification method isrecrystallization from acetic anhydride. Acetic anhydride closesreactive anhydride rings. However, removal of acetic acid produced issometimes difficult. Washing with ether or MTBE can be used to removethe residual acetic acid. The dianhydride crystals generally requiredrying in a vacuum oven. An alternate method is to quickly wash thecrystals with dry ethanol to remove open anhydride rings and then torapidly dry the washed powder in a vacuum oven. This method works forpurifying BPDA if the incoming purity is at least approximately 96%.

[0097] The condensation reaction is performed to the poly (amic-acid)stage. One mole of diamine is reacted with about 1.005 to 1.01equivalents of dianhydride. Excess dianhydride is generally preferablyused to ensure that the dianhydride reagent determines the end group ofthe reaction product, the dianhydride excess ensuring that polymerchains are terminated with anhydride end groups which are known tomaximize stability of the polymer product. In addition, such an excesscompensates for traces of water which can react with anhydride groups.

[0098] The solution is preferably about 15 to 20 weight % total in NMPsolvent. The diamine is usually dissolved first, preferably undernitrogen, although this is not required for all diamines. Thedianhydride is then added. A large scale reaction preferably adds thedianhydride in portions because there is some heat of reaction and it isdesirable to keep the temperature below 40° C. For example, a smallscale reaction of 50 grams could add the dianhydride all at once,provided there is good initial mixing.

[0099] The dianhydride generally dissolves much more slowly than thediamine. For a small-scale reaction, the best and simplest way toperform the reaction is to use a cylindrical jar with apolytetrafluoroethylene sealed cap. This jar can be shaken by hand inthe beginning and then put on a rolling mill at slow speed to turn thejar smoothly. The reaction proceeds best at room temperature over a twoto twelve hour period. Once the initial reaction is complete, asevidenced by a substantially constant solution color and viscosity, thesolution is ready for imide ring closure.

[0100] The chemical reaction to form the polyimide from the poly(amic-acid) can be performed with 1.1 equivalents of acetic anhydrideper imide ring and 1 equivalent of pyridine as a ring closure catalyst.Pyridine can be added and rolling preferably continued until mixed. Theacetic anhydride can cause a portion of the amic-acid polymer toprecipitate.

[0101] The polymer should be redissolved before heating. One needs tocarefully heat the jar to more than 80° C. but less than 90° C. It isbest to use an oven and occasionally remove the jar to shake. Heating isperformed for 60 minutes at full heat or until the color changes arecomplete. The jar is put on a rolling mill to cool while turning. Oncethe solution returns to room temperature, a fully imidized polymerdissolved in NMP results. However, the solution generally also has someresidual pyridine, acetic acid, and may include some acetic anhydride.The solution is expected to be stable for reasonable periods of time.

[0102] A preferred method for collecting the product from a small-scalereaction is to precipitate the polymer into methyl alcohol. This removesthe solvent load and traces of monomers that did not react. It also canbe used, in conjunction with the observed viscosity, to estimate thequality of the polymerization. A good, high molecular weight polyimidewill precipitate cleanly into methyl alcohol with little or nocloudiness. The viscosity should be high (e.g. 8000 to 10,000 cp).

[0103] The precipitated polymer is preferably washed two or more timesuntil the smell of pyridine is slight. The polymer can then be air driedfor a few hours in a hood and then dried in a vacuum oven at 125° C.overnight. The volume of methyl alcohol is preferably about a gallon per100 grams of polymer.

[0104] On a larger scale, water can be used to remove solvents or tracematerials. However, water is expected to be a less efficient than methylalcohol for this purpose. A final soak with methyl alcohol is preferablyadded before drying if water is used with large quantities of polymer.

[0105] In another aspect of the invention which is preferably used toform the battery used in the card cell, a two piece battery assembly isdisclosed. The two piece assembly comprises overcoating an electrodewith a PME to form an electrode/separator and subsequent assembly withan anode.

[0106] In a conventional “gel” electrolyte technology a cathode slurryof electrochemically active material, conductive carbon and binder ismixed in a bulk solvent with the solvent functioning as a plasticizerfor the binder material. The slurry is coated upon a current collectorsubstrate and the bulk solvent removed. The anode is typicallycarbonaceous and made from a slurry of graphite, binder and plasticizingsolvent. The bulk solvent is removed after coating on the currentcollector. The separator is coated as a free standing film from a slurryof non-ionically conductive polymer binder, inorganic support fillermaterial and plasticizing solvent. The cathode, separator and anode areplaced together and laminated unider heat and pressure. The remainingplasticizer is then removed via an extraction process typicallyutilizing a hot solvent. The cell is removed and a liquid electrolyte isintroduced into the system to fill the “pores” created via removal ofthe plasticizer. The cell is then packaged in a foil packaging material.Thus, conventional assembly processes comprise the joining of threeseparate components.

[0107] In contrast, in the two piece battery assembly a cathode slurryof active material, conductive carbon, polyimide binder and lithium saltis mixed in a bulk solvent. The slurry is coated upon a metal currentcollector substrate and the solvent is removed. Subsequently, the coatedcathode is overcoated with a PME comprising a mixture of polyimide,lithium salt and bulk solvent, and then dried to remove solvent with aneffective amount of solvent retained for conductivity purposes, such as5 to 50 weight % versus polyimide plus salt. At this point theovercoated cathode has become both the cathode and the PME separator. Ananode layer is then placed over the PME coated cathode, thus providing abattery assembly using only two components.

[0108]FIG. 7 shows a preferred assembly “folding” process related to thetwo component battery assembly process described above. A PME coatedcathode on a cathode current collector is first provided as describedabove. Prior to placing the anode on the PME separator/cathode, in step710 the surface of the PME overcoated cathode is sprayed with a smallamount of solvent for adhesion purposes. In step 720 a Li anode, such asa Li metal strip having an area slightly less than the area of the PMEcoated cathode is then placed on the PME coated cathode. Alternatively,for a graphitic anode, the anode could also be coated, dried, thenovercoated on the PME coated cathode. An anode tab, such as a nickeltab, is then placed on the anode in step 730. A cell fold is thenperformed in step 740 by wrapping the PME coated cathode over thelithium metal anode (or graphitic anode) as shown in FIG. 7. In step 750a bicell battery 755 having an anode tab which is ready for packaging isproduced. Bicells provide twice the capacity of conventional cells whilehaving the same footprint of the conventional cell.

[0109]FIG. 8 shows an assembly process for packaging the electrochemicalbicell 755 produced by the assembly process shown in FIG. 7, where thesteps of the assembly process shown in FIG. 7 are repeated on the top ofFIG. 8 for convenient reference. Although the process shown in FIG. 8 isapplied to a bicell battery, the described process is in no way limitedto bicells. For example, standard cells according to the invention canbe packaged as shown in FIG. 8.

[0110] In step 810 packaging frame material is rolled out from asuitable roller, the frame material being a material such as PET, havinga thickness substantially the same as the battery itself to fit aroundthe battery. In step 820 an opening is created in the frame materialwhich is slightly larger than the cell 755 to be inserted using a windowpunch or equivalent. A registration hole is also shown which can becreated in step 820.

[0111] Tab sealant is applied to the package frame material orpre-applied to the tab strip. In step 830 a cathode tab is fed, cut andapplied to the frame material. Lower packaging material having a lowtemperature heat sealant and moisture barrier is then applied to theframe. The interior heat sealant layer is a material that not only heatseals to itself, but also bonds strongly to the current collector of thebattery, and preferably activates at between about 90 C to 100 C. Thecell 755 is then preferably pick and placed into the cavity formed bythe punched out package frame and onto the lower packaging materialattached to the bottom of the frame in step 840. The lower packagingmaterial is preferably heated (e.g. 90 C) prior to placing the cell 755thereon to promote adhesion. Upper packaging material having a lowtemperature heat sealant and moisture barrier, which can be the samecomposition as lower packaging material, is then applied in step 850.Optionally, a binder material can be included on the outside of thelower and upper packaging material for applications such as theinsertion of the packaged cell into a credit card.

[0112] Instead of using a perimeter seal used in a conventionalstep-down seal process, the entire surface of the battery along with theperimeter of the packaging material is heat laminated in step 860 toform a finished bicell battery 865 having substantially the samethickness dimension throughout. Although assembly of only a singlebicell is shown, the assembly process shown in FIG. 8 can package one ormore cells in a single package. A lamination temperature such as 110° C.for typically 5 to 15 seconds under a pressure sufficient to produce auniform heat seal but not too high as to distort the battery and/or thepackage is used to provide the lamination to form the finished bicellbattery 865. The substantially constant thickness of bicell 865facilitates integration into a card, such as a credit card, and alsoreduces surface defects.

[0113] As used herein, “substantially the same thickness dimensionthroughout the battery” refers to a thickness over the entire area ofthe packaged battery being ±1 mil. A totally laminated battery withpackage 865 results which behaves as a single laminated layer.

[0114] Although not shown in FIG. 8, a step-down seal process which doesnot utilize a frame can be used. Instead, an elastomeric laminationplate set is used. This allows intimate contact of the packagingmaterial all over the surface of the battery, the packaging materialnecking down to the side seal area where the packaging materiallaminates to itself.

[0115]FIG. 9 shows an assembly process for embedding a packaged bicell865 produced by the assembly process shown in FIG. 8 and an electronicflex circuit embedded inside a PVC card, according to an embodiment ofthe invention. For insertion of the finished packaged cell into a card,a binder adhesive is applied over the outer aluminum foil protectantlayer, such as melamine or PET. However, if the upper and lowerpackaging material include a binder on their exterior as describedabove, this step is unnecessary. This “exterior” binder adhesivepreferably maintains a higher temperature sealant activation than theinterior heat seal layer described above, such as a 110 C to 140 Cactivation. The exterior binder is formulated to adhere well to both theouter battery package material and industry standard credit card PVC orother similar sheet material.

[0116] In the preferred embodiment as shown in FIG. 9, the bicellbattery 865 and flex circuit 980 are then placed in step 910 between PVCsplit cores 915 and 920 which have suitable pockets provided for fittingbicell battery 865 and flex circuit 980. Bicell battery 865 can beconnected to flex circuit 980 before or after placement of the samebetween PVC cores. Pockets in the PVC cores 915 and 920 are preferablymilled, molded or formed to equal depth such that bicell 865 and flexcircuit 980 extend the same distance into each PVC core. Attached to theside of the respective PVC cores 915 and 920 opposite to bicell battery865 and flex circuit 980 are graphics print layers 925 and 930 eachhaving a 2 mil PVC overlay layer 935, 940 to protect the ink.

[0117] The respective components and then subjected to a standard hotlamination process used in the credit card industry, such as atemperature of 125 C to 140C, at a pressure of 200 to 250 psi, for adwell time of 5 to 15 minutes. The battery 855 and flex circuit 980laminate to the interior of the PVC card and the PVC (or other cardmaterial) will laminate to itself to form a card cell article thatbehaves as a single article as it is bound together throughout vialamination. Generally, the finished card cell including the embeddedbattery 865 and flex cell 980 provides a thickness uniformity over theentire area of the card within a range of +1 ml. Thus, once cooled andprocessed into a finished card, the embedded battery is be practicallyinvisible to a surface inspection of the card, and thus has a veryminimal, if any, “witness mark”.

[0118] The IC card device including battery according to the inventionhas been found to withstand rigorous ISO testing. Specifically, cardcells according to the invention have demonstrated compliance withrigorous ISO testing criteria for bending, flex, and torsion accordingto ISO standards ISO/IEC 10373 and 14443 without inducing any detectabledelamination. Moreover, following ISO testing, the bicell battery 865and flex circuit 980 both remain invisible to the external of the cardthus demonstrating no appearance failures of the card cell.

[0119] The high level of thermal stability provided by PMEs according tothe invention permits batteries according to the invention to belaminated at the above-described harsh conditions and show a minimalchange in operating characteristics, such as less than a 2% shift in OCVand a commensurate small change in capacity. Conventional batteriessubjected to the above described card lamination conditions willgenerally either catastrophically fail or experience a large shift inoperating parameters which would render them of no practical use.

[0120] Furthermore, once the card cell is flexed, the battery, package,and PVC all move together as they are bound together through lamination.As a result, flexing does not generate noticeable wrinkles, bumps, edgeeffects, or undulations in the surface of the card.

[0121] Several packaging new packaging aspects are described above. Thebattery package material is laminated to the entire battery. Previouslamination work disclosed only lamination to a portion of the battery.In addition, the invention describes the use of an exterior binderadhesive to laminate the battery to a card material, such as PVC.Previous bonding techniques used to embed batteries in cards havegenerally used a low temperature curable glue because of the inabilityof conventional batteries to withstand typical credit card laminationprocessing conditions. Use of a different activation temperature binders(higher temperature binder for the exterior of packaged cell as comparedto the inside of packaged cell) for battery packaging and batteryintegration into the card allows processing of packaging material havingbinder on its exterior proceed thru the packaging lamination machineryto assemble the battery without causing the exterior binder material tocontaminate the machinery and tooling, as well as preserve its integrityfor the card lamination process. Finally, Installation of a frame tosurround the cell permits production of substantially planar batterieswhich enhances integration into cards.

EXAMPLES

[0122] The present invention is further illustrated by the followingspecific examples. The examples are provided for illustration only andare not to be construed as limiting the scope or content of theinvention in any way.

Example 1 Optical Clarity Measurements for Commercially Availablepolyimide/salt/solvent as Compared to Exemplary PMEs According to theInvention

[0123] The purpose of this example is to demonstrate the homogenousnature of the PME formed from polyimides that have strong interactionswith a lithium salt through demonstrated optical transmission. PME filmswere generated from polyimides shown in FIGS. 1(b), (c) and (m), while aMatrimid 5218 p/salt/solvent was generated for comparison. The PMEs andMatrimid based film were cast upon a clear polyethylene terephthalatesupport film from NMP and dried for three hours in a vacuum oven at 120°C. The residual solvent content was approximately 4 wt %. All PMEcompositions and the Matrimid formulation were 32% polyimide, 64% LiTFSisalt, and the remainder being the small amount of solvent. Allmeasurements were performed using 540 nm light. Film Thickness %Transmission Polyimide Type (mils) Absorbance for a 1 mil film Matrimid5218 0.70 1.903  0.2% FIG. 1(b) Pl 1.68 0.005 99.3% FIG. 1(c) Pl 0.660.000  100% FIG. 1(m) Pl 0.87 0.000  100%

[0124] As demonstrated from the table above, the Matrimid polyimide doesnot form a clear homogenous composition when the lithium saltconcentration is 64%. Moreover, the Matrimid polyimide does not form aclear homogenous composition even at substantially lower saltconcentrations, such at a concentration of 0.5 moles of lithium salt perimide ring provided by the polyimide. Polyimides including a lithiumsalt in a concentration of 0.5 moles (or less) of lithium salt per imidering provided by the polyimide generally lack sufficient minimum ionicconductivity to be a useful electrolyte separator for an electrochemicalcell.

[0125] Although only data for polyimides shown in FIGS. 1(b), (c) and(m) are provided above, all polyimides shown in FIG. 1 ((a) through (m))have been shown to form homogenous, clear films having opticalproperties as shown above for polyimides (b), (c) and (m). This PMEproperty is desired for maximum film stability and ionic conductivity.

Example 2

[0126] Since the PME is a homogeneous or near homogeneous matrixmaterial, batteries formed using the PME exhibit a unique ability tohandle exposure to high temperatures and pressures, and still maintainits performance characteristics. Cell assembly is typically performed atelevated temperatures (e.g. 140° C.) and pressure (e.g. 125 psi) forabout 10 minutes, so subsequent exposures to similar or less rigorousconditions do not effect cells manufactured according to the invention.Significantly, it has been found that cells according to the inventioncan withstand conditions significantly more rigorous as compared to theabove-referenced cell assembly conditions.

[0127] Typical card manufacturing techniques require hot lamination at125° C. for 5 or more minutes in an hydraulic press exerting over 250psi. Batteries according to the invention have demonstrated fullfunction following this process with no significant change in opencircuit voltage (OCV) or capacity following typical laminationprocessing. In contrast, other battery technologies currently availablewill fail to operate (e.g. short) following conventional laminationprocessing or significantly lose capacity and/or OCV.

[0128] Batteries according to the invention can withstand conditionsmore rigorous than typical lamination processing. For example, a batteryaccording to the invention was subjected to an injection molding processto see if the battery could withstand the conditions encountered duringan injection molding process. Injection molding process wereinvestigated for molding the polymers polyethylene-terephthalate (PET)and polyvinyl chloride (PVC) to encapsulate batteries according to theinvention. The PET molding was performed at 295° C. and PVC at 200° C.,with the mold pressure for both processes being 5000 psi. Both testsshowed the batteries according to the invention including a PME, lithiummetal anode and LVO comprising cathode endured the respective injectionmolding processes fully functional, with no significant change incapacity or OCV.

Example 3

[0129] Scanning electron microscope (SEM) micrographs were taken toevaluate the morphology of the PME according to the invention and theinterface between the PME and a lithium vanadium oxide (LVO)/polyimidecathode film. FIG. 10(a) shows two (2) SEM micrographs of the PME alonewhich each evidence a substantially defect free and a porosity freefilm. The thickness of the PME films shown were both about 75 μm.

[0130]FIG. 10(b) shows a SEM of an interface between a PME film (20 μm)disposed on a lithium vanadium oxide/polyimide cathode layer (55 μm).The lower images are blowups of the interfaces shown at the top of FIG.10(b). The interfaces shown are quite uniform and smooth.

Example 4

[0131]FIG. 11 shows the charge/discharge profile of a typical cellaccording to the invention, the cell including a lithium vanadium oxide(LVO) cathode, a Li metal anode and a PME separator, according to anembodiment of the invention. The cell capacity was 25 mAh. The y-axisrepresents cell voltage, while the x-axis represents total time. Thecell demonstrates good cycling stability during a cycling of over 300hours.

[0132] While the preferred embodiments of the invention have beenillustrated and described, it will be clear that the invention is not solimited. Numerous modifications, changes, variations, substitutions andequivalents will occur to those skilled in the art without departingfrom the spirit and scope of the present invention as described in theclaims.

We claim:
 1. An IC card, comprising: at least one plastic layer; abattery and at least one electronic comprising device embedded in saidplastic layer, said battery electrically connected to said electroniccomprising device for providing power for said electronic comprisingdevice; said battery comprising: an anode; a cathode, and at least onepolymer matrix electrolyte (PME) separator disposed between said anodeand said cathode, said PME separator comprising a polyimide, at leastone lithium salt and at least one solvent intermixed, said PME beingsubstantially optically clear.
 2. The IC card of claim 1, wherein saidanode comprises lithium ion intercalation material.
 3. The IC card ofclaim 1, wherein said anode comprises lithium metal.
 4. The IC card ofclaim 1, wherein said anode comprises a lithium metal alloy anode. 5.The IC card of claim 1, wherein a repeat unit weight per imide ring ofsaid polyimide is no more than
 350. 6. The IC card of claim 1, wherein arepeat unit weight per imide ring of said polyimide is no more than 300.7. The IC card of claim 1, wherein a repeat unit weight per imide ringof said polyimide is no more than
 250. 8. The IC card of claim 1,wherein said polyimide is soluble at 25° C. in at least one solventselected from the group consisting of N-methylpyrrolidinone (NMP),dimethylacetamide (DMAc) and dimethylformamide (DMF).
 9. The IC card ofclaim 1, wherein the ionic conductivity of said PME at 25° C. is atleast 1×10⁻⁴ S/cm.
 10. The IC card of claim 1, wherein the ionicconductivity of said PME at 25° C. is at least 3×10⁴S/cm.
 11. The ICcard of claim 1, wherein said Li salt is at least one selected from thegroup consisting of LiCl, LiBr, Lil, LiClO₄, LiBF₄, LiAsF₆, LiPF₆,LiCF₃SO₃, LiBOB, LiN(CF₃SO₂)₂, and lithium bis(trifluorosulfonyl)imide(LiTFSI).
 12. The IC card of claim 1, wherein said cathode comprises anion conducting polymeric binder intermixed with an intercalationmaterial.
 13. The IC card of claim 12, wherein said polymeric bindercomprises at least one polyimide.
 14. The IC card of claim 1, whereinsaid battery provides an open circuit voltage and capacity shift of lessthan 10% following heating at 125° C. for at least 5 minutes while undera pressure of at least 250 psi.
 15. The IC card of claim 1, wherein saidbattery provides an open circuit voltage and capacity shift of less than5% following heating at 125° C. for at least 5 minutes while under apressure of at least 250 psi.
 16. The IC card of claim 1, wherein saidbattery is a primary battery.
 17. The IC card of claim 1, wherein saidbattery is a secondary battery.
 18. The IC card of claim 1, wherein saidbattery is a bicell.
 19. The IC card of claim 1, wherein said lithiumsalt is in a concentration of at least 0.5 moles of lithium per mole ofimide ring provided by said polyimide.
 20. The IC card of claim 1,further comprising a package comprising packaging material surroundingsaid battery to form a packaged battery, said packaging materiallaminated by an exterior binder adhesive to all exterior surfaces ofsaid battery.
 21. The IC card of claim 1, further comprising a packageincluding packaging material surrounding said battery and a frame havingan opening to accommodate said battery therein to form a packagedbattery, wherein said battery is disposed within said opening.
 22. TheIC card of claim 21, wherein said packaged battery provides a thicknessuniformity throughout within ±1 mil.
 23. The IC card of claim 22,further comprising an exterior binder adhesive disposed between saidpackaged battery and said plastic layer to bind said packaged battery tosaid plastic layer, wherein said exterior binder adhesive is activatedat a temperature of at least 100 C.
 24. The IC card of claim 23, whereinan interior binder adhesive seals said battery, wherein said interiorbinder adhesive has an activation temperature which is lower than anactivation temperature of said exterior binder adhesive.
 25. The IC cardof claim 24, wherein said IC card provides a thickness uniformitythroughout within ±1 mil.
 26. The IC card of claim 1, wherein said ICcard complies with ISO testing criteria for bending, flex, and torsionaccording to ISO standards ISO/IEC 10373 and 14443 without inducing anyvisually detectable delamination.
 27. A method of forming a cardincluding embedded electronics, comprising the steps of: providing abattery including an anode, a cathode, and at least one polymer matrixelectrolyte (PME) separator disposed between said anode and saidcathode, said PME separator comprising a polyimide, at least one lithiumsalt and at least one solvent intermixed, said PME being substantiallyoptically clear, and embedding said battery and at least one electroniccomprising device in at least one plastic layer, said batteryelectrically connected to said electronic comprising device.
 28. Themethod of claim 27, wherein said lithium salt is in a concentration ofat least 0.5 moles of lithium per mole of imide ring provided by saidpolyimide.
 29. The method of claim 27, wherein said embedding processcomprises a lamination process, wherein a temperature of least 110° C.for at least 5 minutes under a pressure of at least 200 psi is used forsaid lamination process, said battery providing a shift in open circuitvoltage and capacity of less than 10% following said lamination process.30. The method of claim 27, wherein a temperature of least 130° C. forat least 10 minutes under a pressure of at least 230 psi is used forsaid lamination process, said battery providing a shift in open circuitvoltage and capacity of less than 10% following said lamination process.31. The method of claim 27, wherein said embedding process comprises aninjection molding process, said battery providing a shift in opencircuit voltage and capacity of less than 10% following said injectionmolding process.
 32. The method of claim 31, wherein a temperature of atleast 200° C. and a pressure of at least 1000 psi is used for saidinjection molding process.
 33. The method of claim 32, wherein saidtemperature is at least 250 C and said pressure is at least 5000 psi. 34The method of claim 27, wherein said anode comprises lithium ionintercalation material.
 35. The method of claim 27, wherein said anodecomprises lithium metal.
 36. The method of claim 27, wherein saidcathode comprises an ion conducting polymeric binder intermixed with anintercalation material.
 37. The method of claim 36, wherein saidpolymeric binder comprises at least one polyimide.
 38. The method ofclaim 27, wherein said battery is formed by laminating only two layers,a first layer being said PME disposed on said cathode and a second layerbeing said anode.